FEEDING STRAWBERRIES - Sinclair ProFEEDING STRAWBERRIES Sangral and Sangal Select for strawberries grown in peat modules Fertigation of strawberries using trickle irrigation enables

FEEDINGSTRAWBERRIES

Sangral and Sangal Select for strawberries grown in peat modules

Fertigation of strawberries using trickle irrigation enables both water and feed to be applied regularly and accurately to the crop with minimum wastage. Sinclair has produced a range of products that suit both hard and soft water. Programmes can be tailored to crop requirement with the aid of water analysis.

Crops grown in peat modules, troughs or bucketsCrops grown out of season under protection can increase the growing season considerably. Early and later season crops will complement traditional soil-grown outdoor strawberries with correspondingly higher prices. A further reason for growers using peat-based growing media rather than the soil is the reduction of options to effectively sterilise the soil. Tabletop systems additionally offer growers benefits including improved crop access, reduced harvesting costs and greater pest and disease control.

Peat bags need to have a medium-coarse structure to enable bags to drain well. In addition if darker peat is used this will have the benefit of holding onto easily available water during drying cycles and hot weather, reducing the possibility of the plants wilting. Sinclair growing modules are carefully formulated to fit this requirement, and contain lime to the correct pH and basal fertiliser for around 2 weeks’ growth to ensure rapid rooting. Thereafter liquid feeding will need to provide the nutrients required for a high quality crop.

Growers are advised to have a water analysis to determine the suitability of their water for irrigation purposes before starting feeding. The results will indicate whether additional calcium is required, or if water is hard either to use acid feeds such as Sangral Select, or in cases of extremely hard water to acidify it. Where soft water is used there is usually insufficient calcium present to ensure firm fruit and calcium nitrate needs to be added in a separate tank. Sinclair can arrange for water analyses to be done and give correct advice.

Soft water (bicarbonate level below 80 mg/l)Two tanks are required: one containing Sangral 1-1-3 and one containing calcium nitrate. Feeding would start 2 weeks after planting and continue to beyond picking if the plants are to be kept for a further crop. Plants are fed at every watering. For a second crop nutrient levels have usually dropped to very low levels and feeding would start as soon as new growth is evident. Feed levels are increased from green fruit stage to the end of picking in order to maximise the amount of potash going into the fruit. Potash is essential for fruiting crops and contributes to fruit flavour. Feeding should continue post picking when Elsanta is grown to enable crowns to develop if it is to be kept for a further crop.

Sangral 1-1-3 (8-12-36 + 4 MgO + trace elements)

This product has been specially formulated for strawberries grown in bags and contains the correct ratio of nitrogen, phosphate, potash and magnesium plus trace elements. It contains a low level of nitrogen, which is augmented by calcium nitrate. In the table below the amount of Sangral 1-1-3 required is given, based on a 1000 litre stock tank and a diluter set at 1:100 or 1%.

Table 1: amount of Sangral (kg) required in a 1000 litre stock tank diluted 1:100

Growth stage Sangral 1-1-3 (kg) Conductivity mS/cm*Up to green fruit stage 80 1.02Green fruit to end of picking 100 1.28Post picking to build up crowns 80 1.02

*Conductivity of a solution in distilled water

To the above values the conductivity of the water needs to be added plus the conductivity of any calcium nitrate added.

Calcium nitrate (horticultural / technical grade)

For soft water calcium nitrate needs to be added to ensure good fruit quality. A target of 100 – 120 mg/l calcium is required, and any shortfall in this amount can be calculated from the table below. A separate stock tank is required as the concentrated solution will react with the Sangral 1-1-3 and cause precipitation. It should be noted that some calcium is present in the peat bags from the lime added. When potassium is added from the Sangral this will help to release calcium held in a buffered form in the peat. Sinclair uses a special lime, which also contains magnesium, ensuring the correct Ca: Mg ratio in the growing medium. In the table below horticultural grade calcium nitrate, containing a small quantity of ammonium nitrate, at different concentrations is shown.

N.B. do not use field grade calcium nitrate as this contains a waxy outer coating, which will cause a scum to form in the tank and not dissolve properly

Table 2: calcium nitrate concentration, nutrient content and conductivity

Based on 1000 litre stock tank and 1:100 dilution

kg calcium nitrate in 1000 litres Conductivity*mS/cm

mg/l Ca mg/l nitrate -N mg/l ammonium-N

10 0.10 19 14 120 0.19 38 29 230 0.27 57 43 340 0.36 76 58 450 0.44 95 72 560 0.53 114 86 6


Moderately hard water (bicarbonate level 80 – 120 mg/l)Sangral Select 1-1-3 can be used to acidify water without needing to use acids. This product contains urea phosphate, which acts as a dry acid. When dissolved it produces phosphoric acid in solution which in turn will help to neutralise the bicarbonate present. As before, a water analysis will indicate the level of calcium that may be required. The bicarbonate level is an indication of temporary hardness. If this is high and levels are not reduced the pH of the growing medium will rise over time, causing iron and manganese deficiency. In addition untreated water will cause calcium deposits to build up on drippers, reducing flow rate and causing uneven watering and feeding. Sangral Select 1-1-3 can remove typically 32 - 40 mg/l bicarbonate at dilutions in the table below.

Sangral Select 1-1-3 (9-9-31 + 5 MgO + trace elements)

Table 3: amount of Sangral Select 1-1-3 (kg) required in a 1000 litre stock tank diluted 1:100 (1%)

Growth stage Sangral Select 1-1-3 (kg)

Conductivity mS/cm*

Up to green fruit stage 80 1.16Green fruit to end of picking 100 1.45Post picking to build up crowns 80 1.16


To the above values the conductivity of the water needs to be added plus the conductivity of any calcium nitrate added.

Hard water (120 to 200 mg/l bicarbonate)Water of this hardness generally contains sufficient calcium for the crop’s requirements, but this should still be checked. Sangral Select 3-2-6 is able to remove more bicarbonate from water (typically 67 - 84 mg/l bicarbonate at dilutions in the table below) and contains more nitrogen than Sangral Select 1-1-3. This product is used on its own in a single tank.

Sangral Select 3-2-6 (14-9-30 + 2 MgO + trace elements)

Table 4: amount of Sangral Select 3-2-6 (kg) required in a 1000 litre stock tank diluted 1:100 (1%)

Growth stage Sangral Select 3-2-6 (kg)

Conductivity mS/cm*

Up to green fruit stage 80 1.08Green fruit to end of picking 100 1.35Post picking to build up crowns 80 1.08


Very hard water (bicarbonate levels above 200 mg/l) – using Sangral 1-1-3 plus nitric acidAt this level of bicarbonate Sangral Select products will not be able to sufficiently acidify the water and acidification with nitric acid needs to be considered. It is normal to leave around 50 mg/l bicarbonate to allow some buffering of the water, otherwise the pH of the diluted feed can drop too low.

Ideally an acid dosing system should be used, where a holding tank containing the hard water is dosed to a set point (usually pH 5.8 – 6.0) At this water pH around 50 mg/l bicarbonate remains. Growers do not need to handle the concentrated acid as the dosing is done automatically.

A less accurate alternative is to add the nitric acid to the stock tank. Water analysis can vary over the season and a single analysis in the spring should not be relied upon for a long time – the pH should be checked regularly at the dripper to ensure that the correct amount of acid has been applied. In Table 5 the amount of nitric acid required to remove different levels of bicarbonate is listed. It is important to note that nitric acid will add nitrate-N to the mix, which will need to be accounted for in feed recipes.

Table 5: 60% nitric acid required removing bicarbonate from water. Table assumes 1:100 dilution of stock solution (1%) and 1000 litre stock tank

Bicarbonate to remove mg/l 60% nitric acid needed (litres)

diluted1: 100

Nitrate-N added to mix

mg/l

Conc. acid needed ml per 1000 litres

total irrigation water50 6.2 12 62

100 12.5 24 125150 18.8 36 188200 25.0 48 250250 31.0 60 310300 37.5 72 375

When acidifying very hard water Sangral 1-1-3 would be used – see Table 1.

MonitoringIrrigation systems need to be monitored carefully due to the small root volume of plants in bags – typically 2-6 litres in a 1 metre module containing around 30 litres of growing medium depending on spacing. Changes in pH and conductivity can cause rapid changes in nutrient levels around the roots. On a daily basis the pH and conductivity of the diluted solution at the dripper should be measured, together with the % runoff. In Table 6 the suggested levels of conductivity and runoff are given.

The pH of the applied feed at the dripper should be around 6.0 (suggested range 5.8 – 6.2). If outside these limits then adjust the level of acid if acid dosing, or make slight adjustments to the level of Sangral Select applied. The table assumes increasing feed levels from vegetative growth to fruiting and reducing feed levels from the end of fruiting during crown building stage.

Table 6 : guidelines for conductivity (EC) and runoff at different growth stages

Growth stage EC applied feed mS/cm

EC runoff mS/cm % runoff

After planting for 2 weeks* 0.5 – 1.0 0.8 – 1.2 20 - 30Up to first flowering and early spring regrowth 1.5 – 1.8 1.8 – 2.2 5 - 15Flowering to start of fruiting 1.5 – 1.8 1.8 – 2.2 10 - 20Harvesting to end of growth 1.8 - 1.5 2.2 – 1.8 10 - 25Rest period* 1.5 – 0.5 1.8 – 0.8 0 - 10

*Water only during these stages. EC will depend on irrigation water

If the conductivity of the runoff exceeds 2.2 mS/cm then the strength of feed must be reduced immediately until it reaches the levels in Table 6.

Table 7: analysis of Sangral and Sangral Select grades by %

Sangral 1-1-3 Sangral Select 1-1-3 Sangral Select 3-2-6Total N 8.0 9.0 14.0Ammonium-N 0 0 0Nitrate-N 8.0 7.3 8.6Ureic-N 0 1.7 5.4P2O5 (P) 12.0 (5.2) 9.0 (3.9) 9.0 (3.9)K2O (K) 36.0 (30.0) 31.0 (25.8) 30.0 (25.0)MgO (Mg) 4.0 (2.4) 5.0 (3.0) 2.0 (1.2)B 0.023 0.026 0.026Cu 0.017 0.017 0.017Fe 0.165 0.15 0.15Mn 0.08 0.054 0.054Mo 0.005 0.004 0.004Zn 0.06 0.042 0.042

Table 8: nutrient content of applied solution (100 kg in 1000 litres diluted 1:100)

Sangral 1-1-3 Sangral Select 1-1-3 Sangral Select 3-2-6Total N 80 90 140Ammonium-N 0 0 0Nitrate-N 80 73 86Ureic-N 0 17 54 P 52 39 39K 300 258 250Mg 24 30 12B 0.23 0.26 0.26Cu 0.17 0.17 0.17Fe 1.65 1.5 1.5Mn 0.80 0.54 0.54Mo 0.05 0.04 0.04Zn 0.60 0.42 0.42

Sangral and Sangral Select for fertigating soil grown strawberries

Fertigation of strawberries using trickle irrigation enables both water and feed to be applied regularly and accurately to the crop with minimum wastage. Sinclair has produced a range of products that suit both hard and soft water. Programmes can be tailored to crop requirement with the aid of water analysis. Nutrient requirements for each season will depend on the soil texture, variety and system used. Light soils tend to be low in nitrogen and potash, whereas loam and heavier soils are usually well supplied with these nutrients.

RecommendationsIt is recommended that soil analysis should be undertaken at least every 3 years to monitor nutrient levels, and always before planting a new crop. In the absence of soil analysis the tables below will be of assistance. They assume a Nitrogen SNS Index of 0-1, Phosphate (P2O5 ) index of 2 – 3 and Potash (K2O) index 1-2. Any nutrient deficiency should be rectified as base fertiliser before planting the crop.

Irrigation water should be analysed at least annually including monitoring levels of bicarbonate (temporary hardness), conductivity and pH. The pH of the applied feed should be monitored, and if it is above pH 6.5 the feed will require acid to reduce the pH to 6.5 or below. Sinclair produces acidic feeds (Sangral Select range) which will help to remove bicarbonate from water and ensure that irrigation equipment stays free of calcium deposits.

Feeding the cropsIn the tables below the total requirement is given by growth stage, which can span up to 2-3 months in some cases. The total amount should be split and applied at least twice weekly or more often if possible. At least half of the nitrogen is generally applied before fruiting stage, when leaves are developing, after which potash becomes more important during fruiting stage, potash being important for fruit firmness and flavour. Feeding continues in the case of everbearers through most of the fruiting period, and for June bearers feeding continues beyond the end of picking to encourage new crown development for crops being kept for a further season.

There is now considerable interest in feeding strawberries to conductivity with every irrigation cycle. The crop will take up nutrients applied with every watering more evenly. If a lot of irrigation water is applied between weekly feeds there is a likelihood of nutrient loss by leaching, particularly as strawberries are relatively shallow rooting. To assist, the conductivity of each fertiliser is given at the strength of 1 g/litre, which is a typical amount applied by fertigation. Care needs to be taken that the irrigation water may have a high conductivity, and should always be checked regularly using a conductivity meter. If feeding to conductivity using hard water e.g. in Eastern and Southern England and when using borehole water, the background conductivity needs to be taken into account and added to the conductivity of the fertiliser, otherwise insufficient nutrients will be applied. The system was developed in Holland, where water is generally considered to be soft e.g. rainwater, and soils have low levels of nutrients. In the UK soils generally contain reasonable levels of available nutrients, and levels should be assessed by soil analysis.

Hard water and/or high pH soilsSangral Select soluble fertiliser is ideal for hard water as it’s acidic formulation will help to keep irrigation systems clear of deposits. Sangral Select comes in handy 10 kg bags and contains magnesium and the full range of trace elements. In the tables below nutrients supplied are in kg/ha :

a) Everbearers on light soils

Date (approx.) Sangral Select

Analysis 10 kg bags/ha N P2O5 K2O

May – July 3-1-3 20-7-20 30 60 21 60Aug – Sept 1-1-3 9-9-31 20 18 18 62

Total kg/ha 78 39 122

b) Everbearers on medium and heavy soils



May – July 3-1-3 20-7-20 20 40 14 40Aug – Sept 3-2-6 14-9-30 15 21 14 45


In the next 2 tables feeding continues past the end of cropping in order to build up crowns for the next crop.

c) Maincrop varieties on light soils



April - May 3-2-6 14-9-30 20 28 18 60June - August 3-2-6 14-9-30 20 28 18 60


d) Maincrop varieties on medium and heavy soils





Analysis of Sangral Select grades by %

Sangral Select 3-1-3 Sangral Select 1-1-3 Sangral Select 3-2-6NPK analysis 20-7-20 9-9-31 14-9-30Conductivity mS/cm 1 g/l 1.29 1.45 1.35Total N 20.0 9.0 14.0Ammonium-N 2.3 0 0Nitrate-N 5.6 7.3 8.6Ureic-N 12.1 1.7 5.4P2O5 (P) 7.0 (3.0) 9.0 (3.9) 9.0 (3.9)K2O (K) 20.0 (16.7) 31.0 (25.8) 30.0 (25.0)MgO (Mg) 2.0 (1.2) 5.0 (3.0) 2.0 (1.2)B 0.026 0.026 0.026Cu 0.017 0.017 0.017Fe 0.15 0.15 0.15Mn 0.054 0.054 0.054Mo 0.004 0.004 0.004Zn 0.042 0.042 0.042

Soft water Sangral soluble fertiliser is ideal for soft water. Sangral comes in 20 kg bags and contains magnesium and the full range of trace elements. In the tables below nutrients supplied are in kg/ha :

e) Everbearers on light soils

Date (approx.) Sangral grade


May – July 3-1-3 21-7-24 15 63 21 72Aug – Sept 1-1-3 8-12-36 8 13 19 58


f) Everbearers on medium and heavy soils



May – July 3-1-3 21-7-24 10 42 14 48Aug – Sept 3-1-6 16-5-32 7 22 7 45


In the next 2 tables feeding continues past the end of cropping in order to build up crowns for the next crop.

g) Maincrop varieties on light soils





h) Maincrop varieties on medium and heavy soils





Analysis of Sangral grades by %

Sangral 3-1-3 Sangral 3-1-6 Sangral 1-1-3NPK analysis 21-7-24 16-5-32 7-11-33Conductivity mS/cm 1 g/l 0.82 1.05 1.23Total N 21.0 16.0 8.0Ammonium-N 0 1.0 0Nitrate-N 6.0 9.0 8.0Ureic-N 15.0 6.0 0P2O5 (P) 7.0 (3.0) 5.0 (2.2) 12.0 (5.2)K2O (K) 24.0 (20.0) 32.0 (26.7) 36.0 (30.0)MgO (Mg) 2.0 (1.2) 2.0 (1.2) 4.0 (2.4)B 0.026 0.026 0.023Cu 0.017 0.017 0.017Fe 0.15 0.15 0.165Mn 0.054 0.054 0.08Mo 0.004 0.004 0.005Zn 0.042 0.042 0.06

June 2011

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FEEDING STRAWBERRIES - Sinclair ProFEEDING STRAWBERRIES Sangral and Sangal Select for strawberries grown in peat modules Fertigation of strawberries using trickle irrigation enables